Connecting the mains input to the max turns ie extreme ends of primary winding will reduce the secondary volts somewhat..
Its not worth the trouble rewinding, you will have to be careful to remove the laminated cores...

This is a forum related to chip amps, so discussing about a trafo here wont be a good idea.
PM me and I ll give you a few ideas how to reduce voltages without rewinding or opening the entire E-Core of the trafo.